I have a friend that repairs quilts and she quotes between $150 to $1,000. It all depends on how the extent of the damage and the age of the quilt. It all depends on what the client is willing to pay for the repair. Sometimes after she looks at the quilt and quotes a price they decide against it but she is alright with that. I saw the quilt that she repaired for $800. and the client was very happy because of the sentimental value that the family had for the quilt made by their Grandmother.
I think that since you repaired this quilt you now have an idea of how long it took to repair it. This might give you a way to measure how much time and material it took to finish this project and like others have posted pay yourself by the hour + material. You will find that once you quote your price many will change their mind. Good luck. Stay firm.